Studies are being actively performed for enhancing the light emission efficiency of organic light-emitting devices such as an organic electroluminescence devices (organic EL devices), etc. For example, regarding the light-emitting material for use in a light-emitting layer, development of delayed fluorescent materials is under way as those that can efficiently utilize the excitation energy thereof for light emission. A delayed fluorescent material is a light-emitting material that radiates fluorescence directly from the excited singlet state and radiates fluorescence (delayed fluorescence) also from the excited singlet state formed through reverse intersystem crossing from the excited triplet state, and the excited triplet state can also be made to contribute toward fluorescence emission along with the excited singlet state. As an application of the delayed fluorescent material, there are seen some publications describing an organic electroluminescence device having therein a light-emitting layer formed by a combination of a delayed fluorescent material and a host material.
For example, PTL 1 describes an example of producing an organic EL device having a light-emitting layer that contains 1,3-bis(carbazol-9-yl)benzene (mCP) and a delayed fluorescent material.
PTL 2 describes an example of producing an organic EL device having a light-emitting layer that contains 4,4′-bis(N-carbazolyl)biphenyl (CBP) and a delayed fluorescent material.